Apparatus and process for deslagging steel

ABSTRACT

Apparatus and process for deslagging molten metal such as steel. Molten steel is prepared in a conventional melting furnace and is tapped into a ladle. A vacuum is applied to the slag on the surface of the steel in the ladle by means of an uptake tube containing a thermally insulating paper or refractory lining. The proximity of the uptake tube to the steel-slag interface may be determined by an electrical probe. A chamber couples a vacuum source to the uptake tube, causing the slag to be funneled through the uptake tube until it is deflected by a baffle within the chamber. In an alternative embodiment the uptake tube terminates in a cap having a cross-sectional area substantially equal to the cross-sectional area of the ladle so that the slag is forced through the uptake tube into the chamber. The slag is received in a slag box forming the lower portion of the chamber. A cascade slag trap is provided for collecting that portion of the slag which manages to pass through the chamber. The vacuum source may be of such large capacity that it also provides a vacuum environment for a ladle degassing system.

Haste Sttes Patet 1 3,632,%

[72] Inventor Thomas E. Perry OTHER REFERENCES Chasm Fallstohlo Publication: Bigeev et aL, Metallurg, No. 8, pp. 21- 23, [21] Appl. No. $41,026 Aug 19 5 Flled July 1969 Publication: Oiks et al., Electrometallurgy; STAL 8, Aug., [45] Patented Jan. 4, 1972 1965 635 [73] Assignee Republic Steel Corporation Cleveland Ohio Primary ExaminerGerald A. Dost Attorneys-Robert P. Wright and Joseph W. Malleck [54] APPARATUS AND PROCESS FOR DESLAGGING STEEL ABSTRACT: Apparatus and process for deslagging molten 9 Claims, 8 Drawing Figs. metal such as steel. Molten steel is prepared in a conventional 52 user 266/37, melting furnace and is tapped mm ladle A Vacuum is plied to the slag on the surface of the steel in the ladle by 266,34 v75/4675/49 means of an uptake tube containing a thermally insulating [51] Int. Cl C21c 7/00 paper or refractory lining. The proximity of the uptake tube to [50] Field ofSearch 75/46, 49, the SteeLslag interface may be determined by an electrical 266/34 34 3843 probe. A chamber couples a vacuum source to the uptake 56 R 5 Ct d tube, causing the slag to be funneled through the uptake tube UNITE]; 5. 2:5 LZ until it is deflected by a baffle within the chamber. In an alternative embodiment the uptake tube terminates in a cap having 1,943,307 1/1934 Gilbert 266/34 V a cross-sectional area substantially equal to the cross-sectional 2,202,180 5/1940 3,310,850 3/1967 Armbruter 3,116,999 1/1964 Armbruter 3,206,183 9/1965 Marwick 265/34 R area of the ladle so that the slag is forced through the uptake 266/ 34 V tube into the chamber. The slag is received in a slag box form- 266/34 v ing the lower portion of the chamber. A cascade slag trap is 2156/34 PT provided for collecting that portion of the slag which manages Burch to pass through the chamber The vacuum ource may be of 3,395,903 8/1968 Woodcock 266/34 L such large capacity that it also provides a vacuum environ- Ashburn et a1. R ment for a ladle degassing systenm FOREIGN PATENTS 634,026 8/1959 Italy 266/34V PATENTED JAN 41972 SHEET 1 OF 3 LADLE 20 FROM 1' 20 ,f7 50/: )q LADLE -S LADLL- FURNACE DESL 4665? J DE @4555? con/mm 64 8% LII/Q65 CAPQC/H r VACUUM SOURCE 4/ Ticyl.

v II E INVENTOR. THaM/w E, PE/eer wMz Mw ATfOfA/E/ PATENTED JAN 41972 SHEET 2 OF 3 INVENTOR. THOMAS E. PERRY BY W ATTOE PATENTED JAN 4 I972 SHEET 3 OF 3 v, mm 5 TE 8 p w mi N w APPARATUS AND PROCESS FOR DESLAGGING STEEL BACKGROUND OF THE INVENTION The present invention relates to apparatus and process for vacuum treatment of molten metal, particularly steel, in order to remove the slag portion which forms at the surface of the molten metal after it is prepared in a conventional melting furnace.

It is known in the steel-making art to employ vacuum devices for removing the slag from molten steel, but such devices generally utilize a siphon apparatus wherein a vacuum source is employed to initiate the flow of liquid metal through a narrow siphon tube into a receptacle located at a level beneath the level of the ladle containing the molten steel. There are many inherent deficiencies with these prior art vacuum mechanisms. For example, if the uptake tube disengages from the slag process may become aborted and there will be difficulty in restarting the flow of slag; the devices are too inefficient to transfer large amounts of molten material; when the slag is too viscous it may be difficult to transport it through a narrow siphon tube; slag may build up and eventually close off the flow; and both slag and molten steel may be drawn into the unit. Another deficiency of known processes is the need to continually repair or replace the portion of the uptake tube which enters the slag layer.

Other past methods followed to remove slag are pouring the slag from the ladle, scraping the slag from the molten steel while it is still in the furnace, and allowing a natural flow of the slag through holes in a wall of the furnace. Deslagging the molten steel in the furnace is a long and tedious process, and, more importantly, if slag remains and is present during the subsequent degassing process, that process will be prolonged and the quality of the product will be adversely affected, depending upon the volume of slag present. Similarly, deslagging the steel by pouring it from the ladle requires that the ladle be tilted, resulting in a rapid loss of heat which makes further processing more difficult. Moreover, this method of slag removal cannot always be carried out to completion and the slag removed may contain trapped iron (up to percent or more). Natural flow is also unacceptable in that it does not ensure that the removal of the necessary quantity of slag and adjustment is difficult due to the varying nature and depth of the slag in each batch of steel.

Therefore, it is desirable to provide a process and apparatus which rapidly and efi'iciently removes the slag from molten metal, which is relatively low in cost, which has readily replaceable expendable parts, and which utilizes in part existing facilities in a mill.

SUMMARY OF THE INVENTION An object of the invention is to provide a process and related apparatus to remove the slag from molten metal. In particular, an object is to provide an inexpensive, rapid and efficient method for deslagging steel wherein existing steel mill equipment may be used in part, the mechanism may be easily maintained, and a high quality end product is produced. An object is to provide for the collection of substantially all the slag while preventing gaseous and finely divided solid matter from interfering with the performance of the vacuum source.

To these and other ends, the instant invention contemplates apparatus for deslagging molten metal, including a ladle adapted to contain the molten metal, a chamber and an associated vacuum source adapted to create a vacuum environment to draw the slag from the molten metal, and an uptake tube associated with the chamber and the ladle to funnel the slag from the molten metal to the chamber. In one embodiment of the apparatus a baffle within the chamber opposite the exhaust end of the uptake tube is disposed to deflect the slag so that it does not enter the vacuum source and a slag box located beneath the baffle is disposed to receive the slag after it is deflected by the baffle. An alternative embodiment employs an uptake tube with a flared end cap having substantially the same cross-sectional area as the ladle, the slag being forced up the tube until it flows into the chamber and subsequently into the slag box. A slag trap is included to collect any slag not caught in the slag box.

In accordance with the invention, the ladle containing molten steel, for example, previously prepared in a basic oxygen or other conventional melting furnace, is moved into contact with the uptake tube associated with the chamber and fixed relative thereto. The uptake tube includes inner and outer walls, the outer wall being comprised preferably of steel tube, and the inner wall being preferably fabricated from refractory material or multiple layers of thermally insulating paper which may be readily and periodically replaced. An additional wall fabricated from multiple layers of paper may be disposed about the lower portion of the outer wall. Associated with the uptake tube is an electrical probe for determining the proximity of the tube to the molten steel.

Within the chamber is located the baffle, reinforced by a removable steel member or refractory material, and disposed adjacent the connection between the uptake tube and the chamber. On the side of the chamber opposite the uptake tube connection is a connection to the vacuum source, which permits the uptake tube to act as a funnel to transfer the molten slag from the ladle to the chamber. In one arrangement of the apparatus, when the slag enters the chamber, a large proportion of it is deflected by the baffle into the slag box, which has a lining of refractory material and which is located in the chamber beneath die baffle. In an alternative arrangement, both slag and molten metal are drawn up the uptake tube, which has a flared end cap, while the amount of vacuum is maintained at such a level that only the slag flows into the chamber and then into the slag box.

Some of the slag, particularly gaseous and finely divided solid matter, may manage to elude the slag box. A cascade slag trap comprising a series of pipes defining a tortuous path is provided to collect this portion of the slag before it interferes with the operation of the vacuum source.

The vacuum source may be of larger capacity than necessary for the deslagging operation. Thus the same vacuum source and controls may be used for a subsequent vacuum degassing process common in the production of steel BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a diagrammetric view of a process in accordance with the present invention.

FIG. 2 is a side elevational view of representative apparatus in accordance with the present invention.

FIG. 3 is a front elevational view taken along line 33 of FIG. 2.

FIG. 4 is a sectional view taken along line 44 of FIG. 3.

FIG. 5 is an elevational view of the cascade slag trap of the instant invention taken along line 5-5 of FIG. 2.

FIG. 6 is a partial side elevational view of an alternative form of uptake tube of the present invention.

FIG. 7 is a partial sectional view of a modified form of uptake tube of the invention.

FIG. 8 is a partial sectional view of alternative apparatus in accordance with the present invention.

DETAILED DESCRIPTION Referring to FIG. 1, a ladle 20 filled with molten metal such as molten steel from a conventional melting furnace (not shown) is first applied to a ladle deslagger 6 for removal of the slag in the ladle. Following the slag removing operation the ladle is transported to a ladle degasser 7 in which the charge within the ladle is degassed. Both deslagging and degassing are accomplished through the use of a large capacity vacuum source 8 coupled individually to the ladle deslagger 6 and the degasser 7 by valves 8a and 8b respectively. The valves are under the control of a control mechanism 9 which determines which of the deslagger and degasser is coupled to the vacuum source. Thus the single vacuum source 8 supplies the necessary vacuum for removing slag and degassing the charge in these two sequential operations performed on molten metal in order to refine it.

FIGS. 2 to 8 show the details of a ladle deslagger 6 in accordance with the invention. In connection with the deslagging of molten steel, vacuum deslagging in accordance with the present invention is most advantageously performed in connection with molten steel prepared in a basic oxygen furnace. Although producing a steel melt in a basic oxygen furnace is not essential to the process, if the steel should be prepared in an electric furnace, for example, it would be possible merely to scrape the slag from the surface of the melt before further vacuum treatment, although this would be timeconsuming. The deslagger 6 includes a chamber 10 coupled to the large capacity vacuum source 8 of FIG. 1 by a conduit 12 (FIG. so as to create a vacuum environment within the chamber. An uptake tube 14 is coupled at one end 140 to the chamber 10, and has a second end 14b adapted to contact molten slag 16 forming a layer near the surface of molten steel 18 contained within the ladle 20. In one embodiment of the apparatus (FIGS. 27 within the chamber is located a baffle 22 (FIG. 4) disposed such that molten slag 16 being funneled through the uptake tube 14 is deflected by the baffle 22 into a slag box 26 forming a part of the chamber 10 and located beneath the baffle 22. In the embodiment shown in FIG. 8, the uptake tube 14 is flared at its lower end to form an end cap 15 having substantially the same cross-sectional area as the ladle 20. The vacuum causes both the slag 16 and the molten steel 18 to rise within the uptake tube 14 until the slag is caused to flow into the chamber 10 and then into the slag box 24. A baffle 22 may also be used with this arrangement to protect the vacuum system. A cascade slag trap 26 is further provided between the chamber 10 and its associated vacuum source 8 to prevent any slag which does not fall into the slag box 24 from entering into and interfering with the operation of the vacuum source 8.

The chamber 10 is a generally cylindrical housing formed in three sections and fabricated from a relatively heat resistant and high-strength material, e.g. steel. Thus, the chamber 10 comprises an open-ended cylindrical wall portion 28, tapered outwardly toward its power portion when disposed in an upright position so that slag entering the chamber 10 near its top will not stick to the walls of the chamber; a cover portion 30 of generally circular shape and concave in the direction of the interior of the chamber Ill; and the slag box 24 which forms the lower end of the chamber 10. Cooperating annular flanges 28a and 300, located on the peripheries of wall portion 28 and cover portion 36, respectively, provide a means for bolting together the wall portion 28 and the cover portion 30. Similarly, cooperating annular flanges 245a wall portion 28, respectively, are arranged so that the slag box 24 may be readily and detachably secured to the wall portion 28 of the chamber 10 at its lower extremity (which will be described in more detail below). Vacuum from the vacuum source 8 is introduced into the chamber 10 by means of an annular pipe 32 which enters the chamber ll) near the upper extremity of the wall portion 28.

Diametrically opposite the pipe 32 which permits the vacuum to be introduced within the chamber 10 is an aperture 33 in the wall portion 28 communicating with the uptake tube 14. The uptake tube is employed to funnel slag 16 from the ladle to the chamber 10. The uptake tube may be formed in two sections, a short section 14a permanently secured to the chamber 10 and disposed about the aperture 33 in the wall portion 28, and a longer section 14b designed to penetrate into the molten slag l6 and which is readily removable from the short section 14a so that the apparatus may be easily relocated, or repaired. In addition, different lengths of the longer sections may be used with various sizes of ladles. It should be noted that the uptake tube 14 is preferably substantially straight, as if the tube should be bent or goosenecked, the molten slag 16 passing at high speed through the tube will tend to rapidly disintegrate the wall of the tube at the point of curvature. Preferably also, the short section 14a of the uptake tube 14 flares outwardly toward the aperture 33 so that the velocity of the slag 16 passing through the uptake tube decreases and the baffle 22 erodes less rapidly.

The uptake tube 14 shown in FIGS. 2 and 4 is comprised of an inner wall 14d and an outer wall and is beveled outwardly at its lower end. The outer wall 140 is fabricated from a material capable of withstanding the high temperature of the molten material being funneled therethrough, e.g. preferably steel tube, but may also be graphite, a ceramic material, or the like, and is permanent in nature. The inner wall portion 14d is fabricated from multiple layers of char-resistant paper and is adapted to be disposed within and secured to the outer wall 140 to insulate the uptake tube 14 and to prevent the uptake tube 14 from collapsing upon evacuation under high temperature. The inner wall is temporary in nature. In more detail, the char-resistant inner wall 14d comprises a preformed lining fabricated from a spirally wound strip of thermally insulating paper, e.g. Kraft paper, layers of paper interleaved with layers of asbestos, or other impregnated paper or paperlike material. The inner wall 14d is designed to have only a short life, i.e. about 5 minutes or a long enough period to funnel all the slag 16 from the ladle 20 of molten steel, and to be readily removable and replaceable. The inner wall 14d should be approximately one-half inch in thickness, which is adequate to withstand the flow of slag for the time necessary to funnel the slag 16 from the ladle 20 to the chamber 10. The inner wall is disposed within the outer wall 140 throughout the entire length of the outer wall 140 from end 14 a to end 14b and is held in place only at its bottom end by refractory cement or other suitable adhesive. An additional wall portion He may be disposed about and secured to the outer wall portion 140 near the end portion 14b of the uptake tube 14 which penetrates the slag 16 contained within the ladle 20. This additional wall portion Me may also be fabricated from multiple layers of thermally insulating paper or other suitable material but need only cover the outer wall Me for a distance from the end 1% of the uptake tube 14 sufficient to protect the tube against direct contact with the slag, i.e. about l2 to 14 inches, the usual depth of the slag 16. The inner wall 14d and the additional wall portion Me may be fabricated in one piece, being connected at their lower ends by paper connecting piece 14f which also serves the function of protecting the outer wall 14c from deterioration. If the inner wall 14d and the wall portion 14c are not constructed integrally, the lower portion of the outer wall 14c should be protected by a suitable adhesive or the like.

Alternatively, the long section 14b of the uptake tube 14 may terminate in a cylindrical cup 17 located at the lower end of the tube and adapted to be disposed within the molten slag 16, as shown in FIG. 7. The cup 17 may be fabricated from thermally insulating paper, e.g. of the type used for inner wall 14d, or additional wall portion 142 and is intended to be discarded after removing the slag from one ladle of molten metal. The purpose of the cup 17 is to provide a smoother (less turbulent) entrance of the slag 16 into the uptake tube 14.

Located near the end 14b of the uptake tube 14 which penetrates into the slag 16 is a probe 34 for determining the proximity of the uptake tube 14 to the steel-slag interface. The probe 34 is coupled to an electrical source (not shown) and relies upon the difference in conductivity of the molten steel 18 and the slag 16 to signal when the probe, which is disposed approximately one-quarter inch below the end 14b of the uptake tube 14, has contacted the molten steel 18. Thus a predetermined amount of the slag may be removed without removing any of the molten steel.

As the uptake tube 14 is preferably stationary relative to the chamber 10, and the deslagging apparatus desirably remains fixed in one position, it becomes necessary that the ladle 20 be transported and raised until the slag portion 16 contained within the ladle 20 contacts the end 14b of the uptake tube 14. An operator may easily position the ladle 20 by means of positioning arms 36 that movably support the ladle. The operator may manipulate the ladle 20 such that the uptake tube 14 contacts the slag l6 uniformly about the surface of the molten liquid, i.e., such as a vacuum cleaner is moved about a floor being cleaned. In order to bring the molten slag 16 closer to the open upper end of the ladle 20, the ladle may be tilted before the vacuum is applied by means of the uptake tube 14. Depending upon the viscosity of the slag layer, movement of the ladle may not be necessary. It should be understood, however, that the deslagging apparatus may also be moved into contact with the ladle 20. It is ordinarily easier for the operator to position the ladle with respect to the deslagging apparatus as part of the ladle movement from the furnace in which the steel is prepared to the ladle degassing station, which is normally a part of the process for producing highquality steel.

Disposed within the chamber 10 is the baffle 22, which is suspended from the cover portion 30 in a position directly opposite the aperture 33 communicating with the uptake tube 14. Thus the baffle 22 may deflect slag which has been rapidly funneled by the uptake tube 14 into the chamber 10 from a path which would permit the slag to enter the pipe 32, which is disposed diametrically opposite the aperture 33 and which connects the vacuum source 8 to the chamber. As the baffle 22 is directly in the path of rapidly moving, high-temperature slag, it is necessary to reinforce the baffle with a suitable member 38, e.g., a removable steel member or refractory material, to lengthen the life of the baflle. Although the reinforcement member 38 is not necessary to the operation of the deslagging apparatus of the present invention, it is more economic to utilize a replaceable massive block on the baffle 22 than to make the baffle 22 massive itself. The baffle 22 should not be disposed too close to the aperture 13 as the rapidly moving slag will cause the baffle to disintegrate too quickly.

Another method of preventing the rapidly moving slag from striking the baffle 22 at too fast a rate is illustrated in FIG. 6. A stream of gas, e.g. inert nitrogen gas or air, may be introduced transversely to the flowing molten slag by means of a pipe 19 and a valve 21 connecting a source of inert gas or air or both (not shown) to the short section 14a of the uptake tube 14 at a point close to the aperture 33 of the chamber 10. The inert gas or air deflects the molten slag 16 from its path of travel to prevent the slag from impinging too vigorously against the baffle 22. The inert gas or air is preferably introduced into the pipe 19 at a pressure of about 20 pts.i.g.

In a modified form of apparatus of the present invention, the long section 14b of the uptake tube 14 terminates in a flared substantially cylindrical end cap 15, as shown in FIG. 8. The end cap 15 of the modified embodiment is comprised of an outer wall 15a fabricated from the same material as the uptake tube 14 and an inner wall 15b fabricated from thermally insulating material, e.g. thermally insulating paper such as that used to form inner wall 14d or additional wall portion 14c, or, preferably, a refractory material.

The end cap 15 has substantially the same cross-sectional area as the ladle and is just able to be disposed within the ladle. The end cap is partially immersed within the molten material. The pressure acting on the portion of the molten slag and metal outside the perimeter of the end cap 15 is counterbalanced by the weight of the vertical column of metal of unit cross-sectional area and of a height the same as the difference in levels between the slag outside the end cap and the upper end of the uptake tube (designated d in FIG. 8) plus the pressure within the chamber 10. Both the slag 16 and molten metal 18 are allowed to rise within the uptake tube 14. By carefully controlling the vacuum level produced by the vacuum source 8, only the slag will be drawn ofi the top of the uptake tube 14 and will enter the chamber 10.

That is, the pressure difference between the chamber and the surface of the slag layer outside the end cap 15 is controlled (by regulation of the vacuum source 8) so that it is sufficient to support a column filling the uptake 14 of slag alone or molten metal and slag but not molten metal alone. In this way the pressure difference forces slag (floating at the top of molten metal) upwardly and outwardly through the uptake tube into the chamber until all slag within the end cap has been removed. At this point the uptake tube is filled with molten metal and a small amount of slag at the the upper end. The vacuum may be controlled so that the pressure difference is not great enough to support any more molten metal in the uptake tube, and hence the movement of molten material out the uptake tube ceases. In this wall all the slag but no molten metal is forced out the uptake tube. The vacuum within the chamber may be varied during this operation so as to provide a rapid flow of slag initially (higher vacuum) followed by a slowing of slag flow (lower vacuum) toward the end of the operation to ensure that no molten metal is withdrawn into the chamber.

Preferably, the ladle 20 is raised relative to the uptake tube 14 as the molten slag is removed. The end cap 15 may be disengaged from the molten metal in the ladle 20 when any of the molten metal begins to flow into the chamber 10, thus breaking the vacuum and allowing the remaining molten metal in the uptake tube 14 to run back into the ladle 20. There is no necessity for the receptacle for the slag to be disposed at a level beneath that of the ladle 20. The present apparatus does not utilize the same principle as a vacuum-initiated siphon, since in the instant device the vacuum is continuously in operation.

The baffle 22 may also be used with this embodiment to prevent slag being drawn into the pipe 32 in the event that the vacuum is initiated at too high a rate. Thus, it is desirable to maintain a baffle 22 within the chamber 10 regardless of which form of apparatus is employed in order to avoid interference with the vacuum system.

After the slag 16 has been deflected by the baffle 22 within or has flowed into the chamber 10, a large proportion of the slag is received within the slag box 24 comprising a part of the chamber 10 and located beneath the baffle 22. The slag box 24 is adapted to be readily removed from the chamber 10 upon its being filled. To this end, a plurality of wing-nut-andbolt mechanisms 40 are employed to secure the slag box 24 to the lower periphery of the wall portion 28 of the chamber 10 at the corresponding annular flanges 24a and 28b. The slag box 24. may be transported away from and into its position in the deslagging apparatus by a transfer crane 41, for example. As the slag box 24 is adapted to contain molten slag 16, it should be lined with refractory brick 42 or other suitable material, although by the time the slag 16 is received within the slag box 24, the slag has substantially decreased in temperature.

While the slag box 24 receives the great proportion of the slag l6 removed from the ladle 20, some of the slag, particularly gaseous and finely divided solid matter, may manage to elude the slag box 24 and find its way to the pipe 32 which connects the vacuum source 8 to the chamber 10. To prevent this portion of the slag from subsequently entering into and interfering with the operation of the vacuum source 8, the cascade slag trap 26 is provided to collect this slag. The cascade slag trap 26 comprises a series of vertical pipes 42 and 44 having their lower end portions sealed with caps 46 and 48 designed to catch the portion of the slag which settles in the pipes. In operation (as best seen in FIG. 5), the gaseous and finely divided solid matter of the slag enters the pipe 32, which has a horizontal portion 32a leading to the cascade slag trap 26 and a downwardly directed open-ended vertical portion 32b disposed within the first vertical pipe 42 of the cascade slag trap. Substantially all of the slag matter existing from the open end of the vertical portion 32b of the connecting pipe 32 settles on the cap 46 at the base of the vertical pipe 42. However, some of the slag matter may manage to rise within the pipe 42 and enter the second pipe 44 of the cascade slag trap 26 at the point of connection of the pipes 42 and 44 near their upper ends. Again substantially all the remaining slag matter will settle on the cap 48 at the bottom of the second pipe 44. Extending from the central region of the second pipe 44 is a horizontal pipe 50 which leads directly to the vacuum source 8 through a flexible connector 52 and a valve 54. The valve 54 corresponds to the valve 8a shown in FIG. 1. In this case, the valve 54 is manually controlled. Although a cascade slag trap 26 containing two vertical pipes 42 and 44 is illustrated, it should be understood that one pipe may be sufficient to settle a substantial portion of the slag matter. A plurality of pipes will increase the efficiency of the system while not hindering the maintaining of the vacuum. Thus a tortuous path is provided to collect the portion of the slag not received by the slag box 24 before it can enter into and interfere with the operation of the vacuum source 8.

The entire deslagging apparatus may be supported by a pair of flanges 60, 62 located on the wall portion 28 of the chamber 10 which rest upon a pair of horizontal high-strength I-beams 56, 58.

The vacuum source 8 is preferably of larger capacity than necessary for adequately deslagging the molten steel 18. if the vacuum source 8 is of sufficiently large capacity, it may be used to provide a vacuum environment for the ladle vacuum degassing system. Common controls may also be utilized to determine the application of vacuum, as shown and described above in connection with FIG. 1. Thus both the slag portion 16 and the gaseous matter contained within the molten steel may be removed from the steel while the steel remains within the ladle 20. It is further desirable that the vacuum source 8 be of greater than adequate capacity so that a high vacuum may be placed in communication with the chamber 10 when such is desired, rather than having to reduce the pressure gradually. It should be noted that when a probe 34 is employed, a thin layer of slag will remain upon completion of the deslagging process; this is desirable as it provides temporary protection of the molten steel 18 during the time that the ladle 20 is being moved from the deslagging station to the degassing station.

The apparatus of the present invention shown in FIGS. 2-7 allows for intermittent operation near the end of the deslagging cycle, which is helpful in removing the slag 16. As the end point of slag removal is reached, the coupling together of slag and uptake tube is discontinued to prevent sucking molten steel into the chamber 10. The lost remnants of slag are then sucked into the chamber with intermittent coupling of uptake tube and slag. Such intermittent operation is not possible with the alternative arrangement, since one the tube and slag are decoupled no more sucking can take place.

Thus, the present invention provides apparatus and process for deslagging molten steel by removing the slag from the ladle by means of a high vacuum. With either embodiment the vacuum is used substantially throughout the entire operation, not simply to initiate a siphon action as in prior art systems. The instant apparatus and process is rapid and efficient, relatively low in cost, has readily replaceable expendable pans, and utilizes in part existing facilities in a steel mill. The process and apparatus are also adapted to be used in combination with a vacuum degassing apparatus and process.

I claim:

1. Apparatus for deslagging molten metal, comprising:

a. ladle means for containing molten metal that has a layer of slag thereon;

b. chamber means including a connection to a vacuum source for creating a vacuum environment to draw the slag from molten metal contained within said ladle means;

c. uptake tube means comprising a paper tube and having a first end connected to said chamber means and a second end to be disposed in contact with said slag to funnel said slag to said chamber means; and

d. baffle means disposed within said chamber means opposite said first end of said uptake tube means and between said first end and said vacuum source connection, said baffle means having a surface thereof facing said first end which is struck by slag entering said chamber means and which deflects the slag drawn into said chamber means so that it does not interfere with said vacuum source.

2. Apparatus according to claim 1, wherein said paper tube is multiple-layer thermally insulating.

3. Apparatus for deslagging molten metal, comprising:

a. ladle means for containing molten metal that has a layer of slag thereon;

b. chamber means including a connection to a vacuum source for creating a vacuum environment to draw the slag from molten metal contained within said ladle means and further including a slag receiving receptacle located beneath the baffle means of (d);

c. uptake tube means having a first end connected to said chamber means and a second end to be disposed in contact with said slag to funnel said slag to said chamber means;

d. bafile means disposed within said chamber means opposite said first end of said uptake tube means and between said first end and said vacuum source connection, said baffle means having a surface thereof facing said first end which is struck by slag entering said chamber means and which deflects the slag drawn into said chamber means so that it does not interfere with said vacuum source; and

e. means defining a tortuous path for removing slag not received by said slag receiving receptacle.

4. Apparatus according to claim 3, wherein said tortuous path defining means comprises an outlet pipe from said chamber means terminating inside another pipe that is vertically disposed, said another pipe being coupled to said vacuum source.

5. Apparatus for deslagging molten metal, comprising:

a. ladle means for containing molten metal that has a layer of slag thereon;

b. chamber means including a connection to a vacuum source for creating a vacuum environment to draw the slag from molten metal contained within said ladle means;

c. uptake tube means having a first end connected to said chamber means and a second end to be disposed in contact with said slag to funnel said slag to said chamber means;

d. baffle means disposed within said chamber means opposite said first end of said uptake tube means and between said first end and said vacuum source connection, said baffle means having a surface thereof facing said first end which is struck by slag entering said chamber means and which deflects the slag drawn into said chamber means so that it does not interfere with said vacuum source; and

e. means for introducing a stream of gas transverse to the slag being funneled in said uptake tube means to deflect said slag away from said baffle means.

6. Apparatus for deslagging molten metal comprising:

a. ladle means for containing molten metal that has a layer of slag thereon;

b. chamber means including means for connection to a vacuum source for creating a vacuum environment to draw the slag from molten metal contained within said ladle means; and

c. uptake tube means having a first end connected to said chamber means and a second end that includes a flared end cap, said end cap having a cross-sectional configuration substantially equal to the cross-sectional configuration of said ladle means and to be disposed within said ladle means in contact with the slag and metal therein to draw said slag from said ladle means and to transfer it through said uptake tube means to said chamber means.

7. Apparatus according to claim 6, including means for controlling said vacuum source so that the pressure difference between said chamber means and the surface of said slag outside said uptake tube means is sufficient to support a column filling said uptake tube means of slag or slag and molten metal but not molten metal alone.

8. Apparatus according to claim 6, wherein said end cap and said ladle means may be disposed relative to each other such that said end cap is permitted to receive substantially all the slag on the surface of said molten metal.

9. Apparatus according to claim 6, wherein said end cap contains a lining of refractory material. 

1. Apparatus for deslagging molten metal, comprising: a. ladle means for containing molten metal that has a layer of slag thereon; b. chamber means including a connection to a vacuum source for creating a vacuum environment to draw the slag from molten metal contained within said ladle means; c. uptake tube means comprising a paper tube and having a first end connected to said chamber means and a second end to be disposed in contact with said slag to funnel said slag to said chamber means; and d. baffle means disposed within said chamber means opposite said first end of said uptake tube means and between said first end and said vacuum source connection, said baffle means having a surface thereof facing said first end which is struck by slag entering said chamber means and which deflects the slag drawn into said chamber means so that it does not interfere with said vacuum source.
 2. Apparatus according to cLaim 1, wherein said paper tube is multiple-layer thermally insulating.
 3. Apparatus for deslagging molten metal, comprising: a. ladle means for containing molten metal that has a layer of slag thereon; b. chamber means including a connection to a vacuum source for creating a vacuum environment to draw the slag from molten metal contained within said ladle means and further including a slag receiving receptacle located beneath the baffle means of (d); c. uptake tube means having a first end connected to said chamber means and a second end to be disposed in contact with said slag to funnel said slag to said chamber means; d. baffle means disposed within said chamber means opposite said first end of said uptake tube means and between said first end and said vacuum source connection, said baffle means having a surface thereof facing said first end which is struck by slag entering said chamber means and which deflects the slag drawn into said chamber means so that it does not interfere with said vacuum source; and e. means defining a tortuous path for removing slag not received by said slag receiving receptacle.
 4. Apparatus according to claim 3, wherein said tortuous path defining means comprises an outlet pipe from said chamber means terminating inside another pipe that is vertically disposed, said another pipe being coupled to said vacuum source.
 5. Apparatus for deslagging molten metal, comprising: a. ladle means for containing molten metal that has a layer of slag thereon; b. chamber means including a connection to a vacuum source for creating a vacuum environment to draw the slag from molten metal contained within said ladle means; c. uptake tube means having a first end connected to said chamber means and a second end to be disposed in contact with said slag to funnel said slag to said chamber means; d. baffle means disposed within said chamber means opposite said first end of said uptake tube means and between said first end and said vacuum source connection, said baffle means having a surface thereof facing said first end which is struck by slag entering said chamber means and which deflects the slag drawn into said chamber means so that it does not interfere with said vacuum source; and e. means for introducing a stream of gas transverse to the slag being funneled in said uptake tube means to deflect said slag away from said baffle means.
 6. Apparatus for deslagging molten metal comprising: a. ladle means for containing molten metal that has a layer of slag thereon; b. chamber means including means for connection to a vacuum source for creating a vacuum environment to draw the slag from molten metal contained within said ladle means; and c. uptake tube means having a first end connected to said chamber means and a second end that includes a flared end cap, said end cap having a cross-sectional configuration substantially equal to the cross-sectional configuration of said ladle means and to be disposed within said ladle means in contact with the slag and metal therein to draw said slag from said ladle means and to transfer it through said uptake tube means to said chamber means.
 7. Apparatus according to claim 6, including means for controlling said vacuum source so that the pressure difference between said chamber means and the surface of said slag outside said uptake tube means is sufficient to support a column filling said uptake tube means of slag or slag and molten metal but not molten metal alone.
 8. Apparatus according to claim 6, wherein said end cap and said ladle means may be disposed relative to each other such that said end cap is permitted to receive substantially all the slag on the surface of said molten metal.
 9. Apparatus according to claim 6, wherein said end cap contains a lining of refractory material. 